Process for the manufacture of maleic acid imide

ABSTRACT

Continuous, recycle type process for the manufacture of maleic acid imide from maleic anhydride and ammonia by reacting the components in the gaseous phase in the presence of a dehydration catalyst.

United States Patent Riemenschneider Aug. 12, 1975 PROCESS FOR THE MANUFACTURE OF [51] Int. Cl. C07D 207/40 MALEIC ACID IMIDE [58] Field of Search..,. 260/3265 [75] Inventor: Wilhelm Riemenschneider,

Frankfurt am Main, Germany [56] References Cited [73] Assignee Hoechst Aktiengesellschaf t, U ED STATES PATENTS Frankfurt am Main G rmany 3,397,210 8/1968 Michalowicz 260/3265 [22] Filed: Nov. 12, 1970 Primary Examiner-Henry R. Jiles [21] Appl' 89056 Assistant ExaminerBernard l. Dentz Related s. Application Data Attorney, Agent, or F irm-Curtis, Morris & Safford [63] Continuation-impart of Ser. No. 622,399, March 13,

1967, abandoned. [57] ABSTRACT [30] Foreign Application Priority Data Continuous, recycle type process for the manufacture of maleic acid imide from maleic anhydride and ammonia by reacting the components in the gaseous phase in the presence of a dehydration catalyst.

5 Claims, N0 Drawings PROCESS FOR THE MANUFACTURE OF MALEIC ACID IMIDE The present application is a continuation-in-part application of application U.S. Ser. No. 622,399, filed Mar. 13, 1967 now abandoned and relates to a process for the manufacture of maleic acid imide from maleic anhydride and ammonia.

More specifically the present invention provides a process for the manufacture of maleic acid imide which comprises reacting maleic anhydride and ammonia in the gaseous phase while passing them over alumina as dehydration catalyst.

Michalowicz (US. Pat. No. 3,397,210) describes a process for the production of maleic imide from maleic anhydride and ammonia wherein the components are reacted under a subatmospheric pressure of 1 mm of mercury in a molar ratio of 1:1 in the presence of an acidic SiO catalyst containing a small amount of alumina. It is quite obvious that such a process entails considerable drawbacks. Working under highly reduced pressure necessitates apparatus of large dimensions having thick walls. Moreover, expensive pumps are necessary to produce the high vacuum and much energy is required.

The present invention provides a continuous, recycle type process for the manufacture of maleic acid imide from maleic anhydride and ammonia, which comprises reacting maleic anhydride with ammonia in the presence of an inert gaseous diluent at superatmospheric pressure with a substantial molar deficiency of ammo nia to maleic anhydride in the presence of an aluminum oxide catalyst and with relatively low conversions per pass in the range of from 5 to 20 The process of the invention, which is carried out under a superatmospheric pressure in the range of from 1.5 to atmospheres absolute, allows of passing considerably higher. amounts of reaction components through the reactor per unit of time. Moreover, expensive apparatus and high energy costs, as required in the known process for the production of the high vacuum, can be saved.

To carry out the process of the invention maleic anhydride and ammonia are passed over the catalyst in the gaseous state, preferably not in the mixed state. It has proved particularly advantageous to use a deficiency of ammonia. It has been observed that the yields of maleic acid imide noticeably increase when the molar ratio of ammonia to maleic anhydride is in the range of from 1:3 to 1:12.

When a molar deficiency of ammonia is used, the for- .mation of by-products, for example maleic acid monoamide and/or the ammonium salt of said acid is distinctly reduced as can be seen in the table summarizing the results of example 2 to 8. This fact facilitates the further working up and the distillation to obtain pure maleic imide.

ln contradistinction thereto, equimolecular amounts of the reactants are used in the known process. The conversions obtained in this process amount to 64 71 calculated on maleic anhydride, but the remainder of 36 7c obviously consists of undesired byproducts which can no longer be used in the reaction and of combustion losses.

These are the reasons why the conversion rates in the process of the invention are kept low, in the range of from 5 to 20 70, preferably 8 to 14 per pass through the reactor, calculated on maleic anhydride used. The

unreacted starting components are recycled at once into the reactor. In this manner yields over of maleic imide can be obtained, calculated on maleic anhydride, while the losses are kept very low.

The molar ratio of ammonia to maleic anhydride of 1:12 does not represent an absolute limit. The yield can be further increased with mixtures containing a still smaller amount of ammonia, but in this case the conversion rate, calculated on the maleic anhydride, is so low owing to the small amount of ammonia that the process may become uneconomical.

The reaction is especially advantageous when an inert gaseous diluent is used, for example nitrogen, air or hydrocarbons that are gaseous under the reaction conditions, such as methane, gasolines or benzene. Prior to the reaction the inert gas is advantageously added to one of the reactants, suitably the maleic anhydride. In contrast thereto, no diluent is used in the known process.

The reaction temperatures depend on the activity of the catalyst. They are preferably in the range of from to 400C, more preferably to 250C. It is likewise possible, however, to operate at a temperature below 100C or above 400C.

The reaction is carried out at superatmospheric pressure, for example under a pressure from 1.5 to 10 atmospheres absolute.

The residence times can vary within wide limits, those of 0.1 to 0.5 second being preferred.

The gas mixture leaving the reaction zone is cooled so that the reaction components can be separated in the solid or liquid state, especially when inert gases are concomitantly used and depending on the type of cooling. Alternatively, the reaction gas mixture can be freed from the reaction components by washing, if desired after previous cooling. Suitable washing agents are water or organic solvents, for example benzene or ethyl acetate.

The inert gas which has been wholly or substantially freed from the starting components and the final products can be recycled to the reaction zone.

The maleic acid imide separated in the liquid or solid state or in the form of a solution still contains part of unreacted maleic anhydride. The maleic acid imide can be isolated in pure form in usual manner, for example by distillation, sublimation or extraction. Unreacted maleic anhydride, which has been separated, for example by distillation, is reconducted into the reaction zone.

According to a preferred mode of execution of the process of the invention a mixture containing maleic anhydride is used instead of pure maleic anhydride, which mixture originates from a maleic anhydride synthesis. Especially suitable are mixtures obtained in the oxidation of appropriate hydrocarbons such as, for ex ample, benzene or C -hydrocarbons, or in the oxidation of croton aldehyde. After having been mixed with ammonia, the said reaction gases are passed over the dehydration catalyst.

Maleic acid imide constitutes an intermediate for organic syntheses and can be used as monomer or comonomer in the manufacture of polymers. The nitrogen group confers upon the polymers special properties, for example an improved dyeability and thermal stability under load. Maleic acid imide can furthermore be used in the control of pests, for example for killing insects.

Moreover, it has a bactericidal effect and inhibits the growth of cells.

The following examples serve to illustrate the invention.

terminated, the product was removed by melting and distilled under reduced pressure. Maleic anhydride passed at 5758C under a pressure of 5 mm of mercury. Various experiments were carried out under idenreaction was carried out at an internal temperature of 220C. Maleic anhydride (MA) was dropped into the nitrogen current of 2 cubic meters per hour preheated at 140C and passed in the gaseous state over the catalyst together with ammonia at a pressure of 1.8 atmospheres absolute. The gases leaving the furnace were gradually cooled to lC. When the operation was tical conditions, but with different amounts of gases. EXAMPLE 1 (Comparatwe Example) The results of Examples 1 to 8 are summarized in the A glass tube having a diameter of millimeters and following table which illustrates the dependency of the charged with 130 milliliters of granules of A1 0 having conversion and the yield on the molar ratio of ammonia a diameter of 3 to 5 millimeters was placed in a furnace to maleic anhydride.

lix. MA NH molar conversion \'ield per overall yield mole/ mule/ ratio calculated pass caleul. calculated hr hr NH;;:M/\ on MA reacted on MA l ed on MA reacted 0.5 0.5 1 1|.5 0; 0.3 a 5411 2 2 0.5 (1.25 l :3 1.1.3 '4 75 5m 3 0.5 (1.125 I :4 I48 an '.-'1 51%; 4 (L5 ll lli\'-l l 1 llfi 'l 5.: I) (10.4 J 5 as (1.133 1 us '32 7.| 9 no.3 '4 n as 0.10 1 :a 13.3 7.x 2; ms '2 7 as (man 1 a ,5 '4 7.1 (-75 s 0.x (mm 1 1: s5 #2 (ll) 0 70.: '1;

with electric heating. At an internal temperature of What is claimed is: 200C in the catalyst, the following substances were 1. A continuous, recycle type gas phase process for passed per hour through the furnace at a pressure of the manufacture of maleic acid imide from maleic anl.8 atmospheres absolute: 25 hydride and ammonia which comprises reacting maleic a. 2 cubic meters (measured at normal conditions of anhydride with ammonia in the presence of an inert pressure and temperature) of nitrogen preheated at gaseous diluent at superatmospheric pressure with a 140C, substantial molar deficiency of ammonia to maleic anb. 49 grams (/2 mole) of maleic anhydride dropped hydride in the presence of an aluminum oxide catalyst into the hot nitrogen current and and with relatively low conversions per pass in the c. 12 liters of ammonia (about /2 mole). range of from 5 to 20 The gases leaving the furnace were cooled in stages, 2. A continuous, gas phase process for the manufacfirst to 65C and then to 20C, and washed with water ture of maleic acid from maleic anhydride and ammoin a wash tower. After an operating time of 2 hours the nia comprising the steps of: introducing ammonia and gas currents were switched off and the condensers were maleic anhydride to a reaction zone together with a reheated with steam, whereupon the reaction product cycle stream containing unreacted maleic anhydride, melted and flowed out. It was distilled under a pressure said ammonia being presented in such amount as to of 10 to 12 mm of mercury. The first runnings consisted maintain a substantial molar deficiency of ammonia of 77 grams of maleic anhydride. As main product 1 1.2 relative to maleic anhydride; reacting said maleic anhygrams of maleic acid imide (boiling point l20-l25C dride and ammonia in said reaction zone over an alumiunder 10 mm g; melting Point correspondnum oxide catalyst at a pressure of from 1.5 to l0 ating to a conversion of l 1.5 and an overall yield of 54 mospheres b l t at a t rat f f om 100C to of the theoretical, calculated on maleic anhydridC 400C and at a per pass conversion of maleic anhydride reacted, were obtained, while the yield per pass, calcuf 5 t 20%; and separating u rea ted maleic anh lated on maleic anhydride fed, ammount d t0 -3 dride from the mixture formed in the reaction zone and recycling it to said reaction zone. I EXAMPLES 2 to 8 3. The process of claim 2, wherein the molar ratio of ammonia to maleic anhydride IS in the range of from The furnace described in Example 1 was used. The S0 1;3 to 1:12,

4. The process of claim 2, wherein the conversion per pass is in the range of from 8 to 15%.

5. The process of claim 2, wherein, instead of pure maleic anhydride, a gas mixture containing maleic anhydride is used which is obtained in the oxidation of benzene or of C -hydrocarbons or of crotonaldehyde. l l l 

1. A CONTINUOUS RECYCLE TYPE GAS PHASE PROCESS FOR THE MANUFACTURE OF MALEIC ACID IMIDE FROM MALEIC ANHYDRIDE AND AMMONIA WHICH COMPRISES REACTING MALEIC ANHYDRIDE WITH AMMONIA IN THE PRESENCE OF AN INERT GASEOUS DILUENT AT SUPERATMOSPHERIC PRESSURE WITH A SUBSTANTIAL MOLAR DEFICIENCY OF AMMONIA TO MALEIC ANHYDRIDE IN THE PRESENCE OF AN ALUMINUM OXIDE CATALYST AND WITH RELATIVELY LOW CONVERSIONS PER PASS IN THE RANGE OF FROM 5 TO 20 %.
 2. A continuous, gas phase process for the manufacture of maleic acid from maleic anhydride and ammonia comprising the steps of: introducing ammonia and maleic anhydride to a reaction zone together with a recycle stream containing unreacted maleic anhydride, said ammonia being presented in such amount as to maintain a substantial molar deficiency of ammonia relative to maleic anhydride; reacting said maleic anhydride and ammonia in said reaction zone over an aluminum oxide catalyst at a pressure of from 1.5 to 10 atmospheres absolute, at a temperature of from 100*C to 400*C and at a per pass converSion of maleic anhydride of 5 to 20%; and separating unreacted maleic anhydride from the mixture formed in the reaction zone and recycling it to said reaction zone.
 3. The process of claim 2, wherein the molar ratio of ammonia to maleic anhydride is in the range of from 1:3 to 1:12.
 4. The process of claim 2, wherein the conversion per pass is in the range of from 8 to 15%.
 5. The process of claim 2, wherein, instead of pure maleic anhydride, a gas mixture containing maleic anhydride is used which is obtained in the oxidation of benzene or of C4-hydrocarbons or of crotonaldehyde. 